Abstract: In this paper, a novel framework for optimizing the caching of popular user
content at the level of wireless user equipments (UEs) is proposed. The goal is
to improve content offloading over wireless device-to-device (D2D)
communication links. In the considered network, users belong to different
social communities while their UEs form a single multi-hop D2D network. The
proposed framework allows to exploit the multi-community social context of
users for improving the local offloading of cached content in a multihop D2D
network. To model the collaborative effect of a set of UEs on content
offloading, a cooperative game between the UEs is formulated. For this game, it
is shown that the Shapley value (SV) of each UE effectively captures the impact
of this UE on the overall content offloading process. To capture the presence
of multiple social communities that connect the UEs, a hypergraph model is
proposed. Two line graphs, an influence-weighted graph, and a
connectivity-weighted graph, are developed for analyzing the proposed hypergaph
model. Using the developed line graphs along with the SV of the cooperative
game, a precise offloading power metric is derived for each UE within a
multi-community, multi-hop D2D network. Then, UEs with high offloading power
are chosen as the optimal locations for caching the popular content. Simulation
results show that, on the average, the proposed cache placement framework
achieves 12%, 19%, and 21% improvements in terms of the number of UEs that
received offloaded popular content compared to the schemes based on
betweenness, degree, and closeness centrality, respectively.